1. Field of the Invention
The present invention relates to a light receiving circuit, a semiconductor laser device, and an optical pickup device used for an optical information processing, an optical measurement, an optical communication, or an optical recording disk or the like.
2. Background Art
In recent years, as a high-capacity information storage medium used for personal computers or recording a TV broadcast, an optical disk medium to which information can directly written, a so-called recording type optical disk medium has been popularized. The exemplary recording type optical disks include a CD-R and a DVD-R as write-once medium, and a CD-RW, a DVD-RW, and a DVD-RAM as repeatedly erasable/recordable medium.
FIG. 7 is a schematic diagram of an optical pickup device according to the conventional art, wherein FIG. 7A shows an overall configuration and FIG. 7B shows a configuration of a light receiving circuit 100 for LD power monitoring including a photodiode 4 for LD power monitoring and a photocurrent/voltage conversion amplifier 5 for LD power monitoring (for example, refer to Japanese Unexamined Patent Publication (Kokai) 11-41036).
In FIG. 7, reference numeral 1 represents a semiconductor laser diode (hereinafter, referred to as LD); reference numerals 2a, 2b, 2c, and 2d, lenses; reference numerals 3a and 3b, beam splitters; reference numeral 4, the photodiode for LD power monitoring; reference numeral 5, the photocurrent/voltage conversion amplifier for LD power monitoring; reference numeral 6, an actuator; reference numeral 7, an optical disk; reference numeral 8, a photodiode (PD) for tracking servo control; reference numeral 9, a photodiode (PD) for focusing servo control; reference numeral 10, a photocurrent/voltage conversion amplifier for tracking servo control; reference numeral 11, a photocurrent/voltage conversion amplifier for focusing servo control; reference numeral 12, a laser driving circuit; and reference numeral 13, a feedback resistor.
As can be seen from FIG. 7, the I-V amplifiers 5, 10, and 11 are configured as single-stage amplifiers, respectively, but a plurality of amplifiers may be optionally added after these I-V amplifiers.
In the optical pickup device as shown in FIG. 7, light emitting power of the semiconductor laser diode 1, used for reproduction, recording, or erasing of the optical disk 7, needs to be precisely controlled so as to stably emit a light at predetermined light emitting power corresponding to respective modes of reproduction, recording, and erasing.
In the optical pickup device shown in FIG. 7, the beam splitter 3a splits the light emitted from the LD 1, and the photodiode 4 for LD power monitoring receives the split light. A photocurrent as an output from the photodiode 4 for LD power monitoring is then converted into a voltage output by the photocurrent/voltage conversion amplifier 5 for LD power monitoring, and the feedback control to the laser driving circuit 12 is performed through an automatic power control (APC) circuit so that the voltage output may become constant. As a result of this, the light emitting power of the LD 1 is controlled to be constant.
In addition, according to this configuration, while there is provided with the photodiode 4 for LD power monitoring (hereinafter, photodiode is abbreviated to PD) dedicated to detecting the LD power, some optical pickup devices may combine both of a role for monitoring the LD power, and a role of a PD 9 for focusing servo control or the PD 8 for tracking servo control.